Revisiting Motor Efficiency

During the operational lifespan of your facility, the cost of running an electric motor significantly exceeds its initial purchase price. Improving motor efficiency is, therefore, an essential strategy for reducing your plant’s electrical energy costs.

In an article from 2021, I stated: “Purchasing high-efficiency motors can save 2%-8% on energy costs and quickly pays back the increased purchase price. On variable torque load applications (e.g., conveyors, pumps, and fans), replacing valve or damper type controls with a VFD can reduce energy consumption by orders of magnitude.”

Three years later, what has changed? And what remains important regarding motor efficiency at your facility?

Regulation Changes

The Department of Energy released new regulations in 2023 that amended the efficiency standards for electric motors. Compliance with these regulations will come into effect in 2027 and beyond. Key changes include expanded efficiency regulations that cover a broader range of motor horsepower, including small motors (less than 3hP) and large motors (more than 500hP) that were previously exempt. The new regulations also contain more stringent efficiency requirements for TEFC motors commonly used in industrial facilities.

It is important to note that motor efficiency requirements are presented based on full-load efficiency. Lightly loaded motors will have lower efficiency and this effect is experienced most acutely on smaller-horsepower motors. Similarly, motor power factor will decline at lighter loads. This means less effective work is being done (kW) relative to the continued investment in total energy (kVA).

Recommendations

If your facility is considering making a motor swap to improve efficiency, keep these items in mind:

1. Motors that are oversized or underloaded are good candidates for replacement. Right-sizing the motor may have as much impact as improving the nameplate efficiency.
2. Consider replacing standard-efficiency motors that run continuously with a premium-efficiency option.
3. Premium-efficiency motors have a significantly higher inrush factor (9X FLA or more) than the corresponding standard-efficiency motor (6X FLA). This means adjustments to the motor short circuit and overload protection may be necessary to avoid nuisance tripping. If you’re purchasing a premium-efficiency motor as a spare, ensure that a review of the starter settings is part of the commissioning process for the replacement motor.
4. As new products come to market due to changing efficiency standards, take advantage of new opportunities, but also be aware of challenges. Additional horsepower options in the premium-efficiency category will provide opportunities for motor replacement that have not previously been available. This could be especially impactful on large-frame motors that run continuously. The supply chain will adjust, and finding exact replacements for existing motors may become more difficult. This will especially be true for replacement motors on OEM equipment (such as HVAC units) that may have not previously been impacted by these efficiency requirements.
5. When considering a VFD application for increased efficiency, remember to consider the suitability of the motor insulation and wiring for application on a VFD. Interstates recommends inverter-duty motors on all VFD applications. We also suggest using VFD cable where possible, but some installations that combine magnetic conduit and thermoset wire insulation are also acceptable.

Improving motor efficiency at your facility remains important amid new regulations and technological advancements. You can proactively assess and optimize your motor systems by right-sizing, upgrading to premium-efficiency models, and considering VFD applications. These steps will ensure compliance, reduce operational costs, and enhance plant performance. If you’re interested in learning more about motor efficiency and reducing electrical energy consumption at your facility, call us today at 712-722-1662.